The present application is directed toward methods and apparatuses for controlling the airflow around an airfoil having a leading edge device with a flexible flow surface.
Modern high speed, subsonic commercial aircraft typically have wings with a variety of leading edge and trailing edge devices to change the shape of the airfoil as the flight conditions change. Such airfoils can include flexible panels at the airfoil leading edge, as disclosed in U.S. Pat. Nos. 3,994,451; 4,171,787; 4,351,502; 4,475,702; and 4,706,913. Other airfoils include flexible trailing edge panels, such as those disclosed in U.S. Pat. Nos. 4,131,253 and 4,312,486. Other existing devices include variable camber, leading edge Krueger-type flaps, such as those disclosed in U.S. Pat. Nos. 3,504,870; 3,556,439; 3,743,219; 3,910,530; 3,941,341; 4,189,120, 4,189,122; 4,262,868; 4,427,168; 5,158,252; and 5,474,265.
One potential drawback with some of the foregoing devices is that it may be difficult to arrange the devices to move to very high deflection angles and still stow cleanly for level flight. Accordingly, many of the foregoing devices represent a compromise between a desirable high deflection angle at landing and other low speed conditions, and a clean configuration when the devices are stowed. Another potential drawback with some of the foregoing devices is that they may be difficult to integrate with very thin airfoils and/or very thin portions of airfoils. Accordingly, it may be difficult to integrate these devices into high speed airfoils, which typically have a low thickness-to-chord ratio. Furthermore, it may be difficult to integrate these devices with the thin outboard sections of lower speed airfoils.
The present invention is directed toward methods and apparatuses for controlling airflow with a leading edge device having a flexible flow surface. An airfoil in accordance with one aspect of the invention includes a first portion having a first flow surface and a second flow surface facing opposite from the first flow surface. A second portion of the airfoil has a leading edge, with at least a part of the second portion being positioned forward of the first portion. The second portion is movable relative to the first portion between a first position and a second position, with the second position offset from the first position by an angle of about 45xc2x0 or more. The second portion can include a flexible flow surface having a first shape when the second portion is in the first position and a second shape different than the first shape when the second portion is in the second position. A guide structure can be coupled between the first portion and the second portion, for example, to guide the motion of the second portion of the airfoil.
In a further aspect of the invention, the second portion can include a leading edge body and a third flow surface opposite the flexible flow surface. The guide structure can include a crank pivotably coupled to the first portion, a link body pivotably coupled between the crank and the leading edge body, and a first link pivotably coupled between the first portion and the link body. The guide structure can further include a second link pivotably coupled between the crank and the flexible flow surface, a third link pivotably coupled between the crank and the third flow surface, a fourth think pivotably coupled between the link body and the leading edge body, and a fifth link pivotably coupled between the link body and the leading edge body. In another aspect of the invention, the guide structure can include a crank pivotably coupled to the first portion, a slider pivotably coupled to the crank and slidably engaged with the leading edge body, a first link pivotably coupled between the first portion and the slider, a second link pivotably coupled between the crank and the flexible flow surface, and a third link pivotably coupled between the crank and the third flow surface.
An airfoil in accordance with another aspect of the invention can include a first portion, a second portion movably coupled to the first portion and having an inboard leading edge, an inboard flexible flow surface, and an inboard guide structure having an inboard mechanical arrangement. A third portion can be movably coupled to the first portion and can have an outboard leading edge, an outboard flexible flow surface, and an outboard guide structure having an outboard mechanical arrangement different than the inboard mechanical arrangement.
A method for operating an aircraft airfoil having a first portion and a second portion movably coupled to the first portion in accordance with one embodiment of the invention includes moving the second portion relative to the first portion from a first position to a second position, with at least part of the second portion being positioned forward of the first portion and deflected through at least 45xc2x0. The method can further include changing a shape of a flexible flow surface of the second portion as the second portion moves from the first position to the second position.
A method in accordance with another aspect of the invention includes moving the second portion of the airfoil relative to the first portion by actuating a first guide structure having a first mechanical arrangement, and moving a third portion outboard of the second portion relative to the first portion by actuating a second guide structure having a second mechanical arrangement different than the first mechanical arrangement.